Polyimides have long been valued in the market place for the combination of strength, chemical inertness in a wide variety of environments, and thermal stability. In the last few years, electrospun or electroblown non-woven nanowebs made from polyimides have been prepared, for the first time combining the highly desirable properties of polyimides with a highly porous sheet structure.
Copending applications 61/286,618, 61/286,628, and 61/286,623 disclose the use of fully aromatic polyimide nanowebs as separators in Li-ion batteries and other electrochemical cells.
Honda et al., JP2004-308031A, discloses preparation of polyimide nanowebs by electrospinning polyamic acid solution followed by imidization. Many thousands of polyimide compositions are disclosed including aromatic polyimides. Utility as a battery separator is disclosed.
Jo et al., WO2008/018656 discloses use of a non-fully-aromatic polyimide nanoweb as a battery separator in Li and Li-ion batteries.
Hayes, European Patent 0 401 00581, discloses grafting hydrocarbons to the surface of a semipermeable, permselective polyimide membrane.
It is known that polyimides are hydrolytically unstable at temperatures above 100° C. It is also known that adhesion of polyimide films to certain substrates, such as epoxies, often requires use of a specially formulated adhesive between the layers.
For a variety of end uses, it is desirable to be able to modify the surface chemistry of aromatic polyimide nanowebs to improve compatibility, enhance or reduce wettability, protect the surface from chemical attack, all while retaining the porosity of the nanoweb structure.